Concerns of vehicle styling and visibility require that some vehicle glazings have sharp corners (i.e. corners of low radius of curvature). However, in some of the processes employed to produce glazing profiles, it is difficult, if not impossible, to provide the profiles with corresponding sharp corners.
DE 26 46 058 and GB 1 478 714 are documents from the 1970's which disclose methods of forming corners on preformed weather-strips, involving cutting or deforming the existing strip first. However, the use of weather-strips to glaze vehicles is now obsolete, having been superseded by glazing technologies in which the glazing profile is attached to the pane of sheet glazing material (e.g. glass or plastics) before the glazing is placed in an aperture in a vehicle body (previously, the pane, weather-strip, and any fixing strip were all placed in the aperture separately, and assembled therein).
One process currently employed to produce a glazing profile is extrusion, in which the profile is formed in situ on a pane of sheet glazing material by extruding a bead of polymer of a pasty consistency onto the pane, and allowing it to set. The bead is extruded from an extrusion die which is moved around the perimeter of the pane. Difficulties may be experienced with this process when extruding around corners, because the part of the profile towards the outside of the corner (the “outward part”) extends along a longer path than the inward part. Consequently, as it moves around the corner, the outer part of the die requires a greater rate of supply of polymer than the inner part, which may be difficult or impossible to arrange, and the outward part of the profile is likely to be deficient in some respect if extruded with insufficient polymer. These difficulties increase as the radius of curvature of the corner decreases. Furthermore, when it is desired that the profile has a substantially square corner, this shape may be impossible to achieve given that the outer part of the extrusion die necessarily describes an arc of a circle as it turns the corner. Glazing profiles produced by other processes, e.g. edge encapsulation (i.e. moulding directly in situ onto the glass) may also require modification, e.g. local augmentation or completion of the profile. This may for example avoid the cost of machining a complete new mould for a minor variant.
EP-A-524 060 discloses a process and mould for the improvement of a glazing which has a peripheral profile extruded in situ, the profile having a polymer part completing or replacing the profile. The process is especially intended for the situation where a portion of the profile as extruded is badly shaped, e.g. where the start and finish of the extruded profile meet; remedying such portions of the profile is known as “rectification” in the automotive glazing industry. Both the over-moulding and re-moulding of a corner are also described, using a complicated mould comprising upper and lower parts, a bottom plate, sliding plates, jacks, movable sealing slats and cut-outs to compensate for variations in glass size and thickness. However, even with the precautions incorporated in the mould design, the risk of glass breakage remains.
It would be desirable to provide a process and mould for completing or supplementing a glazing profile, which is not only simplified, but also further reduces the risk of glass breakage.
It has now been realised that by dispensing with the requirement for the process to carry out rectification, design constraints are removed, enabling a fresh approach to be taken to the problem of moulding onto the profile.